1. Field of the Invention
The present invention relates to a signal encoding device and a signal encoding method, a signal decoding device and a signal decoding method, a program, and a recording medium suitably applicable to expand a time-series signal limited to a frequency band at an encoding side to wider frequency band at a decoding side.
2. Description of the Related Art
In recent years, it has become possible to compress a tone quality corresponding to a CD (Compact Disc) in data amount of approximately 1/10 of the original CD by using a human's auditory structure in high-efficiency encoding of an audio signal. Products manufactured by using the technology are presently widespread in the market. Recording in a smaller recording medium or transmission through a network is actually performed.
In this high-efficiency compression, independent formats are respectively applied. It is possible to with any degree of freedom control the tone quality and a bit rate at an encoding side within the format range. For example, a mini disc (Mini Disc; MD) (Registered Trademark of Sony Corporation) includes two modes such as LP2 and LP4 to which a same high-efficiency compression technology is applied, as a long-time recording mode. LP4 is compressed to half the compression size with respect to LP2. Accordingly, LP4 has a deteriorated tone quality, but LP4 has a recording time twice that of the LP2.
However, the high-efficiency compression technology is designed and standardized by targeting the definite bit rate and tone quality. Therefore, when the standard (format) is maintained and the bit rate is reduced, the tone quality is drastically deteriorated. Generally, there is provided a method of distributing remained bits to a low-frequency signal by modifying a high-efficiency encoding algorithm at the encoding side and limiting a high-frequency signal so as to solve the problem.
“Information technology—Coding of audio-visual objects—Part3: Audio (ISO/IEC14496-3: 2001)” can be cited as a related art.